Cell Transport
Understanding membranes
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An interesting mystery on how water can kill you:
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Here is a 6 minute clip comparing active and passive diffusion. It is quite dense with info so it may pay to watch more than once to understand. It summarises and compares transport processes.
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PASSIVE TRANSPORT: No energy is needed
Passive Transport
No energy is needed (No ATP) There are 3 main kinds of passive transport.:
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Diffusion
This is quite a cool quick animation of diffusion and one on osmosis. You might like to explore the host website further.... it has some great resources and practice questions as well.
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Some terms to understand:
Experiments and explanations
Links:
Beetroot and Cell membrane experiment
Facilitated diffusion
Diffusion that is helped along the way… using special carrier molecules which are embedded in the cell membrane.
Go to this link
Go to this link
Active Transport
The liquids inside and outside of cells have different substances. Sometimes a cell has to work and use some energy to maintain a proper balance of ions and molecules. The inside of the cell is called the cytoplasm, but can also be called the intracellular area. The surrounding fluid is called the extracellular space. The majority of cells are always "bathed" in this extracellular fluid which is mainly water. Most small molecules freely travel in and out of the cell through the cell membrane's tiny pores by passive transport mechanisms such as osmosis and diffusion.
Note these 2 terms:
Endocytosis: Into the cell; Exocytosis: Out of the cell
However often the cell needs large molecules and may need to get other substances. To do this the cell must use energy. Whenever energy is needed, the cell uses up ATP made during cell respiration.
(Energy is needed - ATP is needed)
The liquids inside and outside of cells have different substances. Sometimes a cell has to work and use some energy to maintain a proper balance of ions and molecules. The inside of the cell is called the cytoplasm, but can also be called the intracellular area. The surrounding fluid is called the extracellular space. The majority of cells are always "bathed" in this extracellular fluid which is mainly water. Most small molecules freely travel in and out of the cell through the cell membrane's tiny pores by passive transport mechanisms such as osmosis and diffusion.
Note these 2 terms:
Endocytosis: Into the cell; Exocytosis: Out of the cell
However often the cell needs large molecules and may need to get other substances. To do this the cell must use energy. Whenever energy is needed, the cell uses up ATP made during cell respiration.
(Energy is needed - ATP is needed)
ACTIVE TRANSPORT: Needs to have energy input to work
Methods of active transport:
1. Protein Pumps: Special proteins are embedded into the cell membrane. these recognise molecules the cell needs. They then actively transport the molecule into the cell using energy. (ATP) 2. Cytosis: 2 kinds: a) Pinocytosis : For liquids (Cell drinking!!) b) Phagocytosis; For solids (Cell eating) 3. Cytoplasmic Streaming: This is how the cell moves material around the inside of the cell. (When diffusion/osmosis is not effective) Cytoplasmic streaming uses energy and is another form of active transport. It is helped by actin, which is like a stretchy substance found in cells. |
Features of Active transport
1. It uses energy in the form of ATP 2. It moves material from a low concentration to a high concentration (In the opposite direction as compared to passive transport) against the concentration gradient 3. It can actively remove substances out of the cell that may be toxic even if in small amounts 4. It can "concentrate substances into the cell, so even if it has a large amount of a substance it needs it can still get more from the area outside. It can move very large molecules through the membrane |
Osmoregulation
Osmoregulation is all about controlling the balance of all the substances in the cells. This is the most important aspect of cell transport as it ensures that the cells all have the correct amounts of water and other materials so that they can function effectively and efficiently.